Gr113808

For our study, the basic experimental environment was assured by the transepithelial chloride transport inhibitor (bumetanide). Thus, the measured electrical properties (potential difference and electric resistance) were based on sodium ion transport. [15] (link)[16] (link)[17] (link)[18] (link) The solutions used during experiments (concentration in mmol/L) were: RF -Ringer fluid (Na 147. Ondansetron, the 5-HT 3 receptor antagonist, was supplied by GlaxoSmithKline (London, UK), while GR113808, the 5-HT 4 receptor antagonist, and other drugs used in this study were supplied by Sigma-Aldrich Ltd., Poznań, Poland.

Real time Ca 2+ measurements was performed on freshly isolated LV-FW myocytes incubated in a physiological tyrode solution (140 mM NaCl, 4 mM KCl, 1 mM MgCl 2 , 5 mM HEPES, 1.8 mM CaCl 2 and 11 mM glucose, pH 7.4). Cardiomyocytes were loaded with the ratiometric Ca 2+ dye, indo-1AM at room temperature during 20 min (2 M, Life technologies, St-Aubin, France) and cell shortening/Ca 2+ transients were recorded using electrical-field stimulation (1 Hz). Sarcomere length (SL) and fluorescence wavelengths emitted at 405 nm (F405) and 480 nm (F480) were simultaneously recorded using the IonOptix ® system (Milton, USA) coupled to a Zeiss microscope (40× oil, 0.36 m/pixel) [24] (link). The approximate [Ca 2+ ] cytosolic was obtained by measuring the ratio F405/F480. In all experiments, 5-HT 4 R was stimulated by a 30 min incubation with the specific 5-HT 4 R agonist, prucalopride (1 M), or blocked with a 30 min preincubation with the specific 5-HT 4 R blocker GR113808 (10 M) (G5918, Sigma-Aldrich, St-Quentin-Fallavier, France) prior to prucalopride stimulation. Ca 2+ waves defined by any spontaneous rise in the fluorescence ratio during the diastolic phase (30 s) were considered as proarrhythmogenic cellular activity. In all experiments, at least 10 cells were recorded per animal. Data were analyzed using IonWizard 6.4 software.